Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Fri, 20 Oct 2017 17:20:28 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Thomas Garnier <thgarnie@...gle.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>,
	"David S . Miller" <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>, Arnd Bergmann <arnd@...db.de>,
	Kees Cook <keescook@...omium.org>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Matthias Kaehlcke <mka@...omium.org>,
	Tom Lendacky <thomas.lendacky@....com>,
	Andy Lutomirski <luto@...nel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Borislav Petkov <bp@...e.de>,
	"Rafael J . Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
	Juergen Gross <jgross@...e.com>, Chris Wright <chrisw@...s-sol.org>,
	Alok Kataria <akataria@...are.com>,
	Rusty Russell <rusty@...tcorp.com.au>, Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Borislav Petkov <bp@...en8.de>,
	"Luis R . Rodriguez" <mcgrof@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Christopher Li <sparse@...isli.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jason Baron <jbaron@...mai.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Dou Liyang <douly.fnst@...fujitsu.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Lukas Wunner <lukas@...ner.de>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Radim Krčmář <rkrcmar@...hat.com>,
	Joerg Roedel <joro@...tes.org>, Rik van Riel <riel@...hat.com>,
	David Howells <dhowells@...hat.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	Waiman Long <longman@...hat.com>, Kyle Huey <me@...ehuey.com>,
	Jonathan Corbet <corbet@....net>, Michal Hocko <mhocko@...e.com>,
	Peter Foley <pefoley2@...oley.com>, Paul Bolle <pebolle@...cali.nl>,
	Jiri Kosina <jkosina@...e.cz>, "H . J . Lu" <hjl.tools@...il.com>,
	Rob Landley <rob@...dley.net>, Baoquan He <bhe@...hat.com>,
	Jan H . Schönherr <jschoenh@...zon.de>,
	Daniel Micay <danielmicay@...il.com>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	virtualization@...ts.linux-foundation.org,
	xen-devel <xen-devel@...ts.xenproject.org>,
	linux-arch <linux-arch@...r.kernel.org>,
	Sparse Mailing-list <linux-sparse@...r.kernel.org>,
	kvm list <kvm@...r.kernel.org>, linux-doc@...r.kernel.org,
	Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v1 06/27] x86/entry/64: Adapt assembly for PIE support


* Thomas Garnier <thgarnie@...gle.com> wrote:

> >>        */
> >> -     cmpq    $.Lentry_SYSCALL_64_after_fastpath_call, (%rsp)
> >> +     leaq    .Lentry_SYSCALL_64_after_fastpath_call(%rip), %r11
> >> +     cmpq    %r11, (%rsp)
> >>       jne     1f

> > This patch seems to add extra overhead to the syscall fast-path even when PIE is
> > disabled, right?
> 
> It does add extra instructions when one is not possible, I preferred
> that over ifdefing but I can change it.

So my problem is, this pattern repeats in many other places as well, but sprinking 
various pieces of assembly code with #ifdefs would be very bad as well.

I have no good idea how to solve this.

Thanks,

	Ingo

Powered by blists - more mailing lists

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.